The primary sound radiating component of a grand piano is its soundboard. The soundboard is horizontally oriented within the piano's case. The bottom of a conventional grand piano is open, so that sound can radiate downward from the soundboard directly to the surface on which the piano rests.
A conventional grand piano has a hinged cover (to be referred to herein as a "top lid") which can be raised into an open position. When the top lid is propped in its open position, sound radiating upward from the soundboard is reflected by the top lid toward the front side of the piano (the curved side of the piano, which is on the right side of a pianist facing the keyboard).
U.S. Pat. No. 4,211,142, issued to Conklin, discloses attachment of a large bottom panel below the soundboard of a grand piano to reflect sound propagating downward from the soundboard toward the rear side of the piano. Conklin's panel reflects sound in the opposite direction than the top lid of the piano to which it is attached. Conklin suggests that the bottom panel can be convex so as to reflect sound toward the ends of the piano (toward the keyboard and away from the keyboard) as well as toward the rear side of the piano. Conklin's bottom panel has hinges 22 along one edge, and Conklin teaches that the hinges can be attached to the piano case, or to brackets connected to the piano case, to enable the panel's free edge to be raised by a cable or chain 25 slightly above floor level during transportation of the piano.
U.S. Pat. No. 2,138,669, issued to Tower, discloses a tone deflector for a grand piano, which consists of a set of slanting vanes 13 fixedly mounted to the piano case under the soundboard. Tower teaches that some or all of the vanes can be mounted in orientations for deflecting sound toward the piano's rear side, and that some or all of the vanes can be mounted in orientations for deflecting sound toward the piano's front side. However, Tower's vanes are very small, and would not have sufficient surface area to project sound efficiently outward from the soundboard. The small size of Tower's vanes would also prevent them from being oriented at the proper angle for projecting sound efficiently outward from the soundboard to typical target areas.
Until the present invention, however, it had not been proposed that a grand piano be provided with a hinged lower lid completely covering the bottom of the piano's case when closed (to protect the soundboard and mute the piano's sound). Nor had it been proposed until the present invention that such a lower lid be lowered into an open position in which it reinforces and focuses the projection of midrange sounds outward from the front of the piano.